363-206-305
Circuit Pack Descriptions
7-86
Issue 3 June 2000
The 28G-U/28G2-U provides an STS-1 electrical interface to a companion 28G-U/
28G2-U OLIU which allows the two OLIUs to be cross coupled.
Receive Direction.
7
In the receive direction, the optical receiver converts the light
pulses from an NRZ-encoded OC-3 signal to equivalent electrical pulses. The
output from the optical receiver goes into a recovery device. The transport
overhead processor circuit accepts the STS-3 bit stream, frames on the incoming
signal, descrambles it, and processes OC-3 transport overhead. The overhead
information is sent to the SYSCTL circuit pack.
The STS-1 output from the transport overhead processor is sent to the STS-1
pointer processor which performs pointer interpretation and generation. The
output of the STS-1 pointer processor is sent to the VT1.5 pointer processor.
STS-1 path overhead and VT1.5 pointer processing is performed. STS-1s that do
not require VT1.5 cross-connections are passed through without VT1.5 pointer
processing or STS-1 path overhead termination. The output from the VT1.5
pointer processor is sent to the STS-1/VT1.5 router. The router cross-connects
the appropriate VT1.5 tributaries and sends two STS-1 signals to the appropriate
Main or Function Unit (MFU) slots and up to 8 VT-Gs to the low-speed slots.
The 28G-U/28G2-U terminates an OC-3 optical signal, converts it to an electrical
signal, frames on and descrambles the signal, and processes the Transport
Overhead (TO).
Control Circuitry
7
The 28G-U/28G2-U OLIU circuit pack interfaces with the BBG8 system controller
(SYSCTL) via the intershelf control interface. The 28G-U/28G2-U OLIU provides
maintenance elements for reporting the status of the circuit pack, status of the
incoming optical and electrical signals, as well as inventory information (
CLEI
code, date of manufacture, etc.). These maintenance elements are used by the
SYSCTL for fault detection and isolation. Conversely, the 28G-U/28G2-U OLIU
responds to control signals from the SYSCTL such as STS-1 routing, VT1.5
routing, protection switching, and LED control commands.
The 28G-U/28G2-U OLIU accesses the SONET transport overhead and routes it
to and from the SYSCTL circuit pack.
Protection Circuitry
7
STS-1 and VT1.5 path protection switching, compliant with SONET specifications,
is provided. The 28G-U/28G2-U OLIU is protection switched by the SYSCTL in
response to an external command, incoming optical signal failure, or internal
equipment fault. The 28G-U/28G2-U OLIU circuit pack is protection switched by
the SYSCTL when the SYSCTL detects a fault on the active 28G-U/28G2-U OLIU,
and the companion 28G-U/28G2-U OLIU is good.
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